Complex compounds of titanium and/or zirconium are used in many industrial fields. In the chemical surface treatment of metals, bright or previously conversion-coated surfaces are passivated, e.g. with solutions of complex fluorides of titanium and/or zirconium in order to achieve a higher resistance to corrosion and a stronger adherence of paints consisting of subsequently applied organic coatings.
Such passivating aftertreatments are followed, as a rule, by a rinsing with de-ionized water. In that case, the passivating agent is carried over by the workpieces into that rinsing bath so that a continuous or discontinuous discarding of rinsing water is required. Legal and environmental requirements necessitate removal of titanium and zirconium before such water is discharged into the environment.